The invention relates generally to dynamoelectric devices such as generators and large motors. More particularly, the invention relates to a dynamoelectric device having a stator bar with an end arm involute portion substantially aligned with a stator core slot and a related method.
Referring to FIG. 1, portions of a stator 100 and a rotor 102 of a conventional dynamoelectric device in the form of a generator 104 are illustrated. Rotor 102 may include any now known or later developed rotor structure. Stator 100 includes a stator core 110 including a plurality of layered punchings 112. As known in the art, stator core 110 includes a number of circumferentially arranged slots 114 that extend in a radial direction relative to an axis Z of stator 100. Each slot 114 has a pair of stator bars 120 positioned radially therein. Stator bars 120 are conductive, metal bars that are covered with a dielectric, and are coupled together so as to create an electrical winding circuit. Each stator bar 120 includes a linear portion 122 for positioning in a slot 114 of stator core 110 and an end arm portion 130 that extends outwardly past stator core 110 and slots 114 to form an endwinding region 128.
Referring to FIGS. 2-3, enlarged perspective views of end winding region 128 of generator 104 (FIG. 1) are illustrated. As shown, each stator bar 120 (FIG. 1) has an elongated cross-section, e.g., substantially rectangular, or oblong, etc. Further, each end arm portion 130 includes an involute-on-cone bend 132 relative to linear portion 122. The involute portion is typically represented by an equivalent radius. That is, end arm portion 130 extends outwardly so as to form a cone shape (actually frusto-conical shape) when juxtaposed with other end arm portions, and extends circumferentially in one direction so as to form an involute portion relative to linear portion 122. Bend 132 is provided such that an end 140 of a stator bar 120 is positioned, for example, approximately 60 to 80 degrees away from slot 114 (FIG. 1), which permits connection of stator bar 120 (FIG. 1) to a radially adjacent stator bar 142 so as to continue the electrical winding circuit.
During assembly, each stator bar 120 (FIG. 1) is positioned relative to adjacent stator bar(s) by radially moving it into a slot 114 (FIG. 1). However, where previous stator bars have been positioned, sides of end arm portions 130 interfere with adjacent end arm portions 130 in involute-on-cone bend 132 during assembly. In order to address this issue, assemblers must flex and stress end arm portions 130, which some times leads to dielectric test failures that require replacement of the failed stator bar.
FIGS. 3-5 illustrate the problem at four locations A-D along an end arm portion 130 of a stator bar 120A to be positioned relative to an end arm portion 130 of an already positioned stator bar 120B (120B and 120C in FIG. 4). In particular, FIG. 4 shows how a linear portion 122 of a stator bar 120 (FIG. 1) is positioned to slide into slot 114, while involute-on-cone bend 132 at positions B or C, as shown in FIG. 3, are positioned so as to be perpendicular to a cone shape 144 (shown as line in FIG. 4) formed by end arm portions 130. As stator bar 120A moves along radial direction of travel X at linear portion 122 at position A so as to slide into slot 114, involute-on-cone bend 132 at position B or C interferes with adjacent stator bar 120B (in circle). FIG. 5 shows a schematic cross-sectional view of a pair of end arms 120A, 120B at all locations A-D as denoted in FIG. 3. In FIG. 5, the initial position of stator bar 120A to be positioned is shown in phantom, while the final position is shown in solid line. At position A, near linear portion 122, as in FIG. 4, stator bar 120A to be positioned relative to an already positioned stator bar 120B can be easily positioned into slot 114 (not shown) without interfering with stator bar 120B. At positions B and C, however, stator bar 120A interferes with already positioned stator bar 120B (in circles) as the stator bar moves along radial direction of travel X. At position D, no interference may be present or is less of a concern due to increased allowable flex.